Ehlers-Danlos syndrome is a group of disorders that affect the connective tissues that support the skin, bones, blood vessels, and many other organs and tissues. Defects in connective tissues cause the signs and symptoms of Ehlers-Danlos syndrome, which vary from mildly loose joints to life-threatening complications.
Previously, there were more than 10 recognized types of Ehlers-Danlos syndrome, differentiated by Roman numerals. In 1997, researchers proposed a simpler classification that reduced the number of major types to six and gave them descriptive names: the classical type (formerly types I and II), the hypermobility type (formerly type III), the vascular type (formerly type IV), the kyphoscoliosis type (formerly type VIA), the arthrochalasia type (formerly types VIIA and VIIB), and the dermatosparaxis type (formerly type VIIC). This six-type classification, known as the Villefranche nomenclature, is still commonly used. The types are distinguished by their signs and symptoms, their underlying genetic causes, and their patterns of inheritance. Since 1997, several additional forms of the condition have been described. These additional forms appear to be rare, affecting a small number of families, and most have not been well characterized.
Although all types of Ehlers-Danlos syndrome affect the joints and skin, additional features vary by type. An unusually large range of joint movement (hypermobility) occurs with most forms of Ehlers-Danlos syndrome, particularly the hypermobility type. Infants with hypermobile joints often have weak muscle tone, which can delay the development of motor skills such as sitting, standing, and walking. The loose joints are unstable and prone to dislocation and chronic pain. Hypermobility and dislocations of both hips at birth are characteristic features in infants with the arthrochalasia type of Ehlers-Danlos syndrome.
Many people with Ehlers-Danlos syndrome have soft, velvety skin that is highly stretchy (elastic) and fragile. Affected individuals tend to bruise easily, and some types of the condition also cause abnormal scarring. People with the classical form of Ehlers-Danlos syndrome experience wounds that split open with little bleeding and leave scars that widen over time to create characteristic "cigarette paper" scars. The dermatosparaxis type of the disorder is characterized by skin that sags and wrinkles. Extra (redundant) folds of skin may be present as affected children get older.
Some forms of Ehlers-Danlos syndrome, notably the vascular type and to a lesser extent the kyphoscoliosis and classical types, can involve serious and potentially life-threatening complications due to unpredictable tearing (rupture) of blood vessels. This rupture can cause internal bleeding, stroke, and shock. The vascular type of Ehlers-Danlos syndrome is also associated with an increased risk of organ rupture, including tearing of the intestine and rupture of the uterus (womb) during pregnancy. People with the kyphoscoliosis form of Ehlers-Danlos syndrome experience severe, progressive curvature of the spine that can interfere with breathing.